Pablo Fosalba, Enrique Gaztanaga

The origin of power asymmetry and other measures of statistical anisotropy on the largest scales of the universe, as manifested in Cosmic Microwave Background (CMB) and large-scale structure data, is a long-standing open question in cosmology. In this paper we analyze the Planck Legacy temperature anisotropy data and find strong evidence for a violation of the Cosmological principle of isotropy, with a probability of being a statistical fluctuation of order ~ 10^-9. The detected anisotropy is related to large-scale directional LCDM cosmological parameter variations across the CMB sky, that are sourced by three distinct patches in the maps with circularly-averaged sizes between 40 to 70 degrees in radius. We discuss the robustness of our findings to different foreground separation methods and analysis choices, and find consistent results from WMAP data when limiting the analysis to the same scales. We argue that these well-defined regions within the cosmological parameter maps may reflect finite and casually disjoint horizons across the observable universe. In particular we show that the observed relation between horizon size and mean dark energy density within a given horizon is in good agreement with expectations from a recently proposed model of the universe that explains cosmic acceleration and cosmological parameter tensions between the high and low redshift universe from the existence of casual horizons within our universe.

Bernard Carr, Florian Kuhnel, Luca Visinelli

We consider constraints on primordial black holes (PBHs) in the mass range $( 10^{-18}$ - $10^{15} )\,M_{\odot}$ if the dark matter (DM) comprises weakly interacting massive particles (WIMPs) which form halos around them and generate $\gamma$-rays by annihilations. The observed extragalactic $\gamma$-ray background then implies that the PBH DM fraction is $f^{}_{\rm PBH} \lesssim 10^{-10}\,( m_{\chi} / {\rm TeV} )^{1.1}$ in the mass range $2 \times 10^{-11}\,M_{\odot}\,( m_{\chi} / {\rm TeV} )^{-3.2} \lesssim M \lesssim 3 \times 10^{11}\,M_{\odot}\,( m_{\chi} / {\rm TeV} )^{1.1}$, where $m_{\chi}$ and $M$ are the WIMP and PBH masses, respectively. This limit is independent of $M$ and therefore applies for any PBH mass function.For $M \lesssim 2\times 10^{-11}\,M_{\odot}\,( m_{\chi} / {\rm TeV} )^{-3.2}$, the constraint on $f^{}_{\rm PBH}$ is a decreasing function of $M$ and PBHs could still make a significant DM contribution at very low masses. We also consider constraints on WIMPs if the DM is mostly PBHs. If the merging black holes recently discovered by LIGO/Virgo are of primordial origin, this would rule out the standard WIMP DM scenario. More generally, the WIMP DM fraction cannot exceed $10^{-4}$ for $M > 10^{-9}\,M_{\odot}$ and $m_{\chi} >10\,$GeV. There is a region of parameter space, with $M \lesssim 10^{-11}\,M_{\odot}$ and $m_{\chi} \lesssim 100\,$GeV, in which WIMPs and PBHs can both provide some but not all of the DM, so that one requires a third DM candidate.

Matan Grinberg, Juan Maldacena

We argue that the proper time from the horizon to the black hole singularity can be extracted from the thermal expectation values of certain operators outside the horizon. This works for fields which couple to higher curvature terms, so that they can decay into two gravitons. To extract this time, it is necessary to vary the mass of the field.